Due to environmental protection regulations becoming more and more stringent, aqueous systems for the coating of articles are becoming increasingly important. The properties of these systems, have to measure up to those of conventional, i.e. solvent-containing, systems. Amongst coldhardening "aqueous lacquers", water-thinnable epoxide resin systems have become increasingly important. These two-component (2C) systems have outstanding properties. The following advantageous properties should be emphasised: no solvent content or only a low solvent content, non-inflammable, no or little odour, easily worked, low sensitivity to wet coats underneath, good drying properties and rapid hardening throughout, very good adhesion to most substrates, very good intermediate coat adhesion, good protection of metals from corrosion and ease of cleaning of operating devices directly after use.
Thus non-ionically dispersed epoxide resin systems in particular, such as those described in DE-A-36 43 751, with aqueous amine-based hardeners such as those disclosed in EP-A-0 000 605, exhibit many of these outstanding properties, so that they have diverse uses as coating media. A disadvantage of these systems, however, is that they do not produce defect-free surfaces for certain lacquer applications.
EP-A-0 387 418 describes hardeners for aqueous epoxide systems, which are produced by the reaction of polyalkylene polyether polyamines with polyepoxide compounds and by reacting the epoxide-functional product which is obtained with primary or secondary polyamines to form an amine-functional final product. These systems are particularly suitable for the production of sealing compositions, adhesives, mouldings and laminates. When used as a primer surfacer or primer coat in a multi-layer coating they have the disadvantage of an unsatisfactory rubbing-down capacity. Due to their pronounced thermoplasticity, the abrasive paper becomes clogged after a short time and the surface is damaged. Moreover, an unsatisfactory resistance to run-off is obtained with these coating media.
DE-A43 44 510 describes aqueous coating media comprising epoxide-based binder vehicles and aminourethane-based hardeners. Coatings produced from these coating media can in fact be rubbed down, but it has been shown that the surface quality is unsatisfactory. The surface quality can in fact be improved by the addition of water-thinnable polyurethane resins, but this is again achieved at the cost of the rubbing-down capacity.